LIMA (Reuters) - A ceremonial plaza built 5,500 years ago has been discovered in Peru, and archeologists involved in the dig said on Monday carbon dating shows it is one of the oldest structures ever found in the Americas.

A team of Peruvian and German archeologists uncovered the circular plaza, which was hidden beneath another piece of architecture at the ruins known as Sechin Bajo, in Casma, 229 miles north of Lima, the capital. Friezes depicting a warrior with a knife and trophies were found near the plaza.

“It’s an impressive find; the scientific and archeology communities are very happy,” said Cesar Perez, the scientist at Peru’s National Institute of Culture who supervised the project. “This could redesign the history of the country.”

Prior to the discovery at Sechin Bajo, archeologists considered the ancient Peruvian citadel of Caral to be one of the oldest in the Western Hemisphere, at about 5,000 years.

Photo: Sechin Bajo

Scientists say Caral, located a few hours drive from Sechin Bajo, was one of six places in the world — along with Mesopotamia, Egypt, China, India and Mesoamerica — where humans started living in cities about 5,000 years ago.

“The dating done by the German archeologists puts it at about 5,500 years,” Perez said of the plaza, which has a diameter of about 46 feet.

Earlier finds near Sechin Bajo had been dated at 3,600 years, and there may be other pieces of the citadel older than the plaza.

“We’ve found other pieces of architecture underneath the plaza that could be even older,” German Yenque, an archeologist at the dig site, told Reuters. “There are four or five plazas deeper down, which means the structure was rebuilt several times, perhaps every 100 to 300 years.”

Hundreds of archeological sites dot the country, and many of the ruined structures were built by cultures that preceded the powerful Incan empire, which reached its peak in the 16th century, just before Spanish conquerors arrived in what is now Peru.

There are so many archeological treasures that tomb robbing is a widespread problem in the Andean country.

Yenque said the scientists are filling in the site with dirt to preserve it and plan to resume excavation of the deeper floors when they get more grants to fund the project.

“We are lucky it was never destroyed by tomb robbers; that is why we are covering it up now,” Yenque said.

A team of archaeologists have discovered the ruins of the oldest known structures in Peru, erected 5,500 years ago, the Lima newspaper El Comercio reported.

The discovery is a sunken, circular plaza, situated in the coastal zone of Casma in the northern Ancash department, which according to 25 carbon-dating tests was first built around the year 3,500 BC. Nearly 2,000 years later, another structure measuring 180 by 120 metres was added onto it, the report said.

Peter Fuchs, director of the Sechin Bajo archaeological project, said the discovery appeared to confirm the first societies in what is now Peru with ceremonial centres in Casma, 300 kilometres north of Lima.

“Whoever built Sechin Bajo had advanced knowledge of architecture and construction. This is clearly seen in the handling given to the materials so that the buildings would be consistent,” Fuchs said. The prime material was stone transported from nearby hills.

The original plaza served for meetings and socialising, the scientists said. A second stage included adjacent buildings, and the final stage resulted in the largest structure with various patios, curved corners and niched walls.